Arbitrary object writes via skipped signature verification
Published Apr 22, 2026 · Updated Apr 22, 2026
Authentication bypass in MinIO's Snowball auto-extract handler allows remote attackers with a valid access key to write arbitrary objects. PutObjectExtractHandler omits authTypeStreamingUnsignedTrailer from its authentication switch, so crafted Snowball PUT requests reach extraction without cryptographic signature verification. Knowledge of an access key and target bucket name is sufficient; accepted tar payloads can create or overwrite bucket objects and consume storage.
Summary
What happened
Authentication bypass in MinIO's Snowball auto-extract handler allows remote attackers with a valid access key to write arbitrary objects. PutObjectExtractHandler omits authTypeStreamingUnsignedTrailer from its authentication switch, so crafted Snowball PUT requests reach extraction without cryptographic signature verification. Knowledge of an access key and target bucket name is sufficient; accepted tar payloads can create or overwrite bucket objects and consume storage.
The record
- CVE
- CVE-2026-40344
- Published
- Apr 22, 2026
- Updated
- Apr 22, 2026
- Vendor
- MinIO
- Product
- MinIO
- Classifications
- CWE-306, CWE-287, T1565.001, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 22, 2026CVE publishedPublication date reported by the CVE source.
- Apr 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=>= RELEASE.2023-05-18T00-05-36Z, < RELEASE.2026-04-11T03-20-12Z
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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